Provided is an underpants-type disposable diaper that is improved in a fit to a part from the intergluteal cleft to the crotch of a wearer and less prone to give a wearer a puffy and discomfort feeling at a crotch portion during wearing.In order to solve the above problem, provided is an underpants-type disposable diaper, wherein the back body part B has at an intergluteal cleft facing portion a bending fit portion 40 which is bent so as to enter into the intergluteal cleft of a wearer, the outer sheet 20 has at each of the front and back body parts F, B a lifting elastic member 26 - - - , 28 - - - which exerts a contraction force of a vertical component to lift a crotch portion toward a waist side, and a tensile stress on the front body part F undergoing vertical elastic deformation is larger than a tensile stress on the back body part B undergoing vertical elastic deformation.
